1. Field of the Invention
The present invention relates to an optical probe for obtaining a micro light spot and an optical pick-up apparatus using said optical probe.
2. Description of the Related Art
In recent years, an optical probe utilizing an optical near field is used for recording information in an optical disk with a resolution not higher than the diffraction-limited of light or for observing the surface of an object to be measured, as disclosed in, for example, publication 1 (S. Mononobe et al.: “Reproducible fabrication of a fiber probe with a nanometric protrusion for near-field optics”, Appl. Opt., Vol. 36, No. 8 (11997) pp. 1496-1500) and publication 2 (Y. Kim et al.; “Fabrication of micro-pyramidal probe array with aperture for near-field optical memory applications”, Jpn. J. Appl. Phys., Vol. 39, No. 3B (2000) pp. 1538-1541). In this optical probe, the distal end side of an optical fiber is sharpened and the side surface the distal end portion is coated with a metal so as to confine the light wave in a micro region so as to obtain a micro spot.
However, the optical probe of this kind gives rise to the problem that, because of the absorption by the metal coated on the side surface, the light throughput efficiency is very low. It is certainly possible to avoid the absorption loss, if the metal coating is not applied to the side surface. In this case, however, the oozing of the light wave from the sharpened distal end portion of the optical fiber is increased, resulting in failure to obtain a micro spot.
As described above, the conventional optical probe having a metal coating applied to the side surface of the sharpened distal end portion of an optical fiber gives rise to the problems that the throughput efficiency of the light passing through the probe is very low and that it is impossible to obtain a desired micro spot unless the metal coating is not applied to the side surface.